174 – II.3. BRASSICA CROPS (BRASSICA SPP.)
B. juncea
B. juncea is believed to have arisen about 10 000 years ago as the result of an
interspecific cross or crosses between plants of B. rapa by B. nigra. Evidence suggests
that one primary centre of origin is China, where the greatest divergence of forms evolved
(Prain, 1898; Sinskaia, 1928; Vavilov, 1949). A second centre of origin is thought to be
Afghanistan and adjoining regions (Olsson, 1960; Mizushima and Tsunoda, 1967;
Tsunoda and Nishi, 1968) from where it spread to a secondary centre on the Indian
subcontinent and became a major oilseed crop (Hemingway, 1995; Prakash and Hinata,
1980). GRIN (USDA-ARS, 2011) lists B. juncea as native to temperate Asia including
China, Kazakhstan, Kyrgyzstan, Mongolia, eastern and western Siberia, Tajikistan and
Turkmenistan. It has been introduced as a condiment crop to Europe, the Americas,
Australia and New Zealand. It has been designated a weed of southern European
Russian Federation, the Caucasus, central Asia and southern Siberia, and a casual or feral
plant in southern and southeast Asia, Africa and America (Canadian Food Inspection
Agency, 2007).
B. carinata
B. carinata, like B. juncea, is believed to have arisen about 10 000 years ago as a
result of an interspecific cross between plants of B. nigra and B. oleracea. The cross is
thought to have occurred in the Mediterranean region where both species were present.
As the climate in North Africa became dryer, B. carinata, along with the flora of the
moist Mediterranean region, moved south to the highlands (1 300-1 500 metres) of
Ethiopia. The species distribution from its Ethiopian centre of origin has been limited to
neighbouring east African countries. Recently it has been introduced as an oil crop to
India and as a species of commercial interest in Canada and Spain.
Ecosystems and habitats where the species occurs natively and has naturalised
There are few areas of the world where members of the family Brassicaceae
are totally absent. The exceptions are the Antarctic and some parts of the tropics.
However, even in the tropics, the family is thinly represented by some introduced
cosmopolitan weeds that have become established. The genera and species of the family
occur in greatest number and diversity in the temperate zone of the northern hemisphere
and in particular, the areas surrounding the Mediterranean basin and throughout the
southwest and central regions of Asia (Figure 3.25) (Hedge, 1976). Although the generic
and specific endemism in the family is highest in the Irano-Turanian region, the centre of
the present-day subtribe, Brassicinae, lies in the Mediterranean basin (Hedge, 1976).
Feral populations in disturbed soils
Due to the large seed losses in commercial B. napus fields and the potential loss
during transport and handling, the surviving seeds give rise to volunteers in subsequent
crops and feral populations in non-cultivated areas (CETIOM, 2000; MacDonald and
Kuntz, 2000; Orson, 2002; Pessel et al., 2001; Price et al., 1996). Volunteers are
controlled by cultivation and herbicide application. In both Canadian and UK trials,
the numbers of genetically modified (GM), herbicide resistant (HR) B. napus volunteers
in the year following GM trials were comparable to, or less than, conventional B. napus
(Crawley et al., 1993; Booth et al., 1996; Hails et al., 1997; Rasche and Gadsby, 1997;
Sweet et al., 1999a, 1999b, 1997; Sweet and Shepperson, 1998; Norris et al., 1999).
In their survey of Canadian commercial fields, MacDonald and Kuntz (2000) found the
same trend, with similar numbers of volunteers in the year following cultivation of
